"…the commonplace shadow does not guarantee visual consistency or permanence, just infinite ambiguity"

‘The Invisible Landscape’ and Planar forms

By separating the represented object into series of planes contrasted by — naturally occurring backgrounds and pitch black shadows, there is an inevitable and more or less consistent progression towards creating three-dimensional objects within a two-dimensional space, a progression in which shadow and object compete with one another to become “delineated planar forms”. This has the effect of creating the ultimate three dimensional illusion within the classical constraints of a photograph.

( quote from: A Rare Synthesis of Realism and Abstraction by Gail Stavitsky)